Propellant compositions



N Drawing.

This invention relates to propellant compositions and more particularlyto propellant compositions useful in the propulsion of rockets.

In the rocket propellant field, red or white fuming nitric acid iswidely used as an oxidizer in conjunction with fuels to yield highenergy propellants which can undergo spontaneous ignition upon mixing.To illustrate, a combination of red fuming nitric acid and hydrazine isconsidered, on the basis or" theoretical thermal calculations, to be avery powerful hypergolic rocket propellant composition. However, liquidfuming nitric acid presents many problems in handling and use because ofits high reactivity, toxicity,and corrosive nature.

It is the principal object of this invention to provide safe to handle,efficient, non-hypergolic fuels and nitrogen oxide containing solidoxidizers which upon mixing as in the combustion of a rocket undergospontaneous deflagration resulting in the release of high energy valuesnormally associated with the interaction of fuming nitric acid and suchfuels. Another object of the present invention is to provide propellantscomprising a non-hypergolic fuel and a non-hypergolic solid oxidizercontaining readily available quantities of oxygen. A further object isto provide a solid nitrogen oxide containing oxidizer which isessentially non-shock sensitive unlike some other solid nitrogen oxidecontaining compounds presently used as propellant oxidizers, e.g.nitronium perchlorate. Other objects and advantages will become apparentfrom the detailed specification presented hereinafter.

I have now discovered that certain solid, complex nitrogen oxide-borontrifluoride coordination compounds selected from the group consisting ofnitronium tetrafiuoroborate (NO BF nitrogen trioxide boron trifiuoridecomplex (N O .BF nitrogen tetraoxide boron trifiuoride complex (N O BFand nitrogen pentoxide boron trifiuoride complex (N O .BF when admixedwith conventional fuels yield propellants having excellent hypergolicproperties. These propellants upon deflagration also produce largevolumes of high temperature gases.

In such mixtures the complex nitrogen oxide boron trifiuoride compoundsbehave chemically much the same as does red fuming or White fumingnitric acid. However, the solid nitrogen oxide-boron trifluoridecoordination compounds by themselves are easily and safely handled,stored and transported as these materials do not have the inherenttoxicity and corrosive nature of the fuming nitric acids.

Fuels which have been found to provide hypergolic compositions uponmixing with the hereinbefore listed complex compounds fall into thefollowing groups:

Group I.Symmetrical and asymmetrical lower alkyl substituted hydrazinesand their salts wherein the lower alkyl groups contain from one to fourcarbon atoms.

Group II.Lower alkyl substituted polyamines wherein the alkyl groupscontain from one to four carbon atoms.

Group 1II.-Aminodiborane (NH B H ammoniaaminodiborane complex (NI-I -NHB H or lower alkyl hydrazine aminodiborane complexes drazine containsfrom one to four carbon atoms.

Group IV.Cellulose, and ether and/ or ester derivaatent tives ofcellulose wherein the molecular species reacted with the cellulosemolecule to form the ether and/or ester are limited to those reactivecompounds containing from one to two carbon atoms.

Group V.-Glycols, glycerols and polyols containing from two to sixcarbon atoms.

All of the aforementioned fuels when combined by simple mixing with thesolid complex nitrogen oxide boron trifiuoride compounds of the presentinvention i.e. NO2BF4, N2O3.BF3, N204-BF3 and N2O5.BF3, undergoextremely vigorous thermal reactions evolving large vol umes of gases.While no action usually occurs immediately upon mixing the oxidizer andthe fuel, after an induction period of from a few up to 30 seconds ormore, a deflagration reaction proceeds instantaneously and almostexplosively.

The amount of fuel that will react stoichiometrically with the oxidizeris dependent upon the replaceable hydroxyl, amino or alkyl substitutedamino groups in a given fuel under the conditions of the reaction.Preferably the amount of fuel and solid oxidizer to be employed in apropellant composition will be such that the ratio of the nitric acidequivalents in the oxidizer to each of the above listed replaceablegroups in a given fuel is from about 1:1 to about 8:1. Desirably a ratiofrom about 2:1 to about 4: 1 will be employed.

The following example is given to more clearly illustrate the inventionbut is not to be construed as limiting it thereto.

Example Nitronium tetrafluoroborate was prepared by the method reportedby Olah, Kuhn and Mlinke (J. Chem. Soc. 1956, 4257-4259).

A propellant composition was prepared by admixing 10 mole parts of thenitronium tetrafiuoroborate with about 2.5 mole parts of dimethylhydrazine hydrochloride. After a short induction period of approximately15 seconds, the mix defiagrated with almost explosive velocity andliberated large volumes of gaseous products. In less than one minute thereaction mixture had consumed itself and only a small amount ofinorganic residue remained.

In a manner similar to that described in the foregoing example,hypergolic compositions result from mixing N O .BF N O .BF or N O .BF(prepared as described by Bachmann and Hokama, J. Am. Chem. Soc. 79,4370 [1957]) with a fuel member selected from the Groups I-V listedhereinbefore, utilizing from 1 to 8 equivalents (on the basis ofequivalent nitric acid values in the oxidizer) for each equivalent ofreplaceable hydroxyl, amino or alkyl amino groups present in said fuelmember. Such mixtures undergo spontaneous deflagration the same as wasexhibited by the nitronium tetrafluoroborate-dimethyl hydrazinehydrochloride mix.

Various modifications may be made in the present invention withoutdeparting from the spirit and scope thereof for it is understood that Ilimit myself only as defined in the appended claims.

I claim:

1. A rocket propulsion method which comprises admixing in a rocketcombustion chamber a fuel member selected from the group consisting of(l) symmetrical and asymmetrical alkyl substituted hydrazines and theirsalts, (2) alkyl substituted polyamines, (3) aminodiborane (NH B H andammonia-amino diborane complex, hydrazine amino diborane (N H -NH B Hcomplex and alkyl substituted hydrazine amino diborane (RNHNH -NH B Hcomplexes wherein R is alkyl and wherein the alkyl substituents of eachof the above listed fuel members contain from 1 to 4 carbon atoms, (4)cellulose, ether derivatives of cellulose and ester derivatives ofcellulose wherein the molecular species reacted with the cellulosemolecule to form the ether and the ester thereof are limited to thosereactants containing from 1 to 2 carbon atoms and (5) polyols containingfrom 2 to 6 carbon atoms and an oxidizer selected from the groupconsisting of nitronium tetrafluoroborate nitrogen trioxide borontrifluoride complex (N O -BF nitrogen tetraoxide boron trifluoridecomplex (N O -BF and nitrogen pentoxide boron trifluoride complexwherein the quantities of said oxidizer and said fuel are such that theratio of nitric acid equivalents in said oxidizer to each of the abovelisted amino, hydroxyl and alkyl substituted amino groups in said fuelmember is from about 1:1 to about 8:1 thereby to produce a vigorous,hypergolic thermal reaction evolving large volumes of gases.

2. A rocket propulsion method which comprises; admixing in a rocketcombustion chamber the oxidizer nitronium tetrafiuoroborate and the fueldimethyl hydrazine hydrochloride wherein the ratio of nitric acidequivalents in said oxidizer to the alkylamine groups in said fuel isfrom 1:1 to about 8:1 thereby to produce a vigorous, hypergolic thermalreaction evolving large volumes of gases.

3. A rocket propulsion method which comprises; admixing in a rocketcombustion chamber the oxidizer nitrogen trioxide boron trifluoridecomplex and the fuel dimethylhydrazine hydrochloride wherein the ratioof nitric acid equivalents in said oxidizer to the alkylamino groups ofsaid fuel is from 1:1 to about 8:1 thereby to produce a vigorous,hypergolic thermal reaction evolving large volumes of gases.

4. A rocket propulsion method which comprises; admixing in a rocketcombustion chamber the oxidizer nitrogen tetroxide boron trifluoridecomplex and the fuel dimethylhydrazine hydrochloride wherein the ratioof the nitric acid equivalents in said oxidizer to the alkylamino groupsin said fuel is from 1:1 to about 8:1 thereby to produce a vigorous,hypergolic thermal reaction evolving large volumes of gases.

5. A rocket propulsion method which comprises; admixing in a rocketcombustion chamber to oxidizer nitrogen pentoxide boron trifluoridecomplex and the fuel dimethylhydrazine hydrochloride wherein the ratioof the nitric acid equivalents in said oxidizer to the alkylamino groupsin said fuel is from 1:1 to about 8:1 thereby to produce a vigorous,hypergolic thermal reaction evolving large volumes of gases.

References Cited in the file of this patent UNITED STATES PATENTSStengel .v Sept. 6, 1960 Zletz et al. Feb. 7, 1961 OTHER REFERENCES

1. A ROCKET PROPULSION METHOD WHICH COMPRISES ADMIXING IN A ROCKETCOMBUSTION CHAMBER A FUEL MEMBER SELECTED FROM THE GROUP CONSISTING OF(1) SYMMETRICAL AND ASYMMETRICAL ALKYL SUBSTITUTED HYDRAZINES AND THEIRSALTS, (2) ALKYL SUBSTITUTED POLYAMINES, (3) AMINODIBORANE (NH2B2H5) ANDAMMONIA-AMINO DIBORANE